2021 IRC Chapter 24 (Fuel Gas)
Lessons 8 through 10 covered how gas gets to an appliance safely: venting, connectors, and piping. This lesson covers where the appliance itself is allowed to sit, and which appliance types carry their own installation restrictions on top of the ordinary rules. GCHS staff run into this most often in rehab work: a gas dryer relocated into a converted closet, a space heater someone installed in a finished bedroom to cut the heating bill, or a range swapped in without checking the clearances on the label. None of this is about GCHS installing equipment. It is about knowing, when reviewing a contractor's scope or walking a finished job, whether the appliance is even allowed where it sits before worrying about how well it was hooked up.
IRC G2406.2 keeps gas appliances out of sleeping rooms, bathrooms, toilet rooms, storage closets, and any space that opens only into such rooms, unless one of its exceptions applies. The main exception is a direct-vent appliance installed per its listing and the manufacturer's instructions: it draws combustion air from outdoors and discharges combustion products outdoors through a sealed system, so the code treats it as though it were located outside the room it heats. The other exceptions are narrower: vented room heaters, wall furnaces, and vented gas fireplaces in a room that meets the required volume criteria of G2407.5; a single wall-mounted unvented room heater with an oxygen-depletion safety system in a bathroom (6,000 Btu/h maximum) or a bedroom (10,000 Btu/h maximum) that meets those volume criteria; and a closet-type space that opens only into a bedroom or bathroom, is used for nothing else, and has a solid weather-stripped self-closing door and outdoor combustion air. This is why a direct-vent gas fireplace is a normal sight in a bedroom while a freestanding vent-free heater is held to tight limits: the two look similar to an occupant but sit on opposite sides of this rule.
Lesson 1 covered G2408 in detail: an appliance with an ignition source installed in a garage has to have that ignition source elevated not less than 18 inches above the garage floor unless the appliance is listed as flammable-vapor-ignition resistant (G2408.2), and an appliance in a private garage must also either sit at least 6 feet above the floor or be protected from motor vehicle impact (G2408.3). The same rules apply to gas appliances specifically, which is where they show up again here: a gas water heater, furnace, or gas-fired unvented heater installed in a garage still needs the 18-inch elevation (unless it is FVIR-listed) and impact protection, on top of whatever clearance and combustion air rules apply to that appliance type. An inspector checking a garage-installed gas appliance is really checking two different chapters at once, G2408 for the ignition-source elevation and whichever equipment chapter governs that appliance's own installation.
An unvented (vent-free) room heater burns gas and releases its combustion products directly into the room rather than through a flue, which is exactly why the code surrounds it with more restrictions than a vented appliance gets. G2445.3 caps an unvented room heater's input at 40,000 Btu per hour, and G2445.4 sends its location back to G2406.2, which allows only a single wall-mounted unvented heater in a bedroom or bathroom, and only where the room meets the code's volume criteria. That heater is capped much lower, at 10,000 Btu per hour in a bedroom and 6,000 Btu per hour in a bathroom, reflecting the smaller air volume and closed-door habits of those rooms. G2445.5 also limits the combined input of all unvented appliances in a room to 20 Btu per hour per cubic foot of room volume. Every unvented room heater, regardless of size or location, must have an oxygen-depletion safety system that shuts off the main and pilot burners once room oxygen falls to the percentage the manufacturer specifies, never lower than 18 percent, and that set point cannot be adjusted in the field. G2445.2 also prohibits using one or more unvented room heaters as the sole source of comfort heating for a dwelling unit; they may supplement a proper heating system, not replace it. In GCHS rehab work, an unvented heater found in a converted bedroom, or one clearly being used to heat the whole house, is a correction item worth flagging even if the unit itself is listed and in good condition.
Lesson 5 covered the exhaust duct side of a clothes dryer in detail: size, material, length limits, and termination. On the gas side, a gas dryer is connected the same way any other appliance is, through an accessible shutoff valve in the same room, within 6 feet, ahead of a listed connector rated for the appliance, following Lesson 10's connector rules. Dryers are one of the appliance types G2419.4 exempts from the sediment trap requirement, since their burner and control design is less sensitive to the debris a trap is meant to intercept. The recurring rehab issue is not the gas connection itself but relocation: when a laundry area moves during a remodel, both the gas connection and the exhaust duct run have to be redone together, and it is common to find one updated and the other left as a legacy installation that no longer meets current length or termination rules.
Gas ranges, cooktops, and wall ovens are installed per their listing and the manufacturer's installation instructions (G2447.1), which set the appliance's own clearances to combustible cabinetry and countertop material, along with any anti-tip bracket requirement for a freestanding range. The code adds a few fixed items: a range on a combustible floor sits on its own base or legs with at least the label clearances (G2447.4), and the cooking top needs 30 inches of vertical clearance to combustible material and metal cabinets, or 24 inches with the protection the code specifies (G2447.5). At a summary level, the inspector's job is less about memorizing side clearances, since they vary by listed appliance, and more about confirming the unit is installed exactly as its own instructions specify: anti-tip device engaged, clearances met, and the shutoff valve and connector following the same rules as any other appliance. A range does not require a sediment trap under G2419.4, and the correct component order from the piping system to the appliance is the shutoff valve first, then the connector, then the appliance, the same order covered in Lesson 10.
IRC R315.2 requires a carbon monoxide alarm wherever a dwelling unit contains a fuel-fired appliance or has an attached garage with an opening that communicates with the dwelling, in new construction and where permitted alterations, repairs, or additions occur. The alarm goes outside each separate sleeping area in the immediate vicinity of the bedrooms, and inside a bedroom that contains a fuel-burning appliance or has one in its attached bathroom (R315.3). Every appliance covered in this lesson, and in Lessons 8 through 10, is exactly the kind of fuel-fired equipment that triggers this requirement. Lesson 13 covers R315 in full detail as part of the life-safety review; for now, the point worth carrying forward is that gas appliance installation and carbon monoxide alarm coverage are reviewed together, not as two separate checklist items.
In the field
A common rehab finding: an occupant has placed a portable or wall-mounted vent-free gas heater in a bedroom to supplement inadequate central heat. Even if the unit is listed and appears well maintained, GCHS checks three things before pricing any related repair work: whether the heater is a single wall-mounted unit with an oxygen-depletion safety system in a bedroom that meets the volume criteria (most freestanding vent-free heaters are not), whether its input rating is at or under the 10,000 Btu/h bedroom cap, and whether it is serving as the home's only heat source, which G2445.2 does not allow regardless of listing. A heater that fails any one of these is a finding to write up, not a fixture to work around.
A quick worked comparison: a homeowner asks whether a 25,000 Btu/h wall-mounted unvented heater can go in a child's bedroom. G2406.2 allows a single wall-mounted unvented heater in a bedroom only at 10,000 Btu/h input or less, so a 25,000 Btu/h unit fails regardless of what its own literature says. The code cap for the intended room always controls, and a mismatch between a heater's rated input and the room it is proposed for is one of the fastest checks an inspector can run before opening the manual at all.
1. Under G2406.2, a gas appliance may be located in a bedroom or bathroom only where an exception applies. Which of these satisfies an exception?
2. An inspector finds a gas water heater, not listed as flammable-vapor-ignition resistant, in a private garage with its igniter 14 inches above the floor. Under G2408.2, this is:
3. Under G2445.3, an unvented room heater's input rating may not exceed:
4. A homeowner wants to install a single wall-mounted unvented gas heater in a bedroom that meets the room volume criteria. Its input rating is capped at:
5. Every unvented room heater, regardless of its input rating or listed location, must have:
6. Under G2445.2, one or more unvented room heaters:
7. A gas clothes dryer's connection to the gas piping system follows the same shutoff and connector rules as other appliances. Which statement is accurate about its sediment trap?
8. A laundry area is relocated during a remodel. The gas connection is updated to the new location but the dryer exhaust duct is left as it was. This is a concern because:
9. For a gas range or cooktop, clearances to combustible cabinetry and countertop material are established primarily by:
10. For a freestanding gas range installed per its manufacturer's instructions (G2447.1), an item an inspector specifically checks beyond gas connection and clearances is:
11. For a gas range installation, the correct order of components from the piping system to the appliance is:
12. Under R315, a carbon monoxide alarm is required in a dwelling unit that:
13. An occupant has installed a 25,000 Btu/h wall-mounted unvented gas heater, marketed for bedroom use, in a child's bedroom. The correct finding is:
14. A vented gas fireplace that is not a direct-vent unit is proposed for a bedroom. Under G2406.2, this installation is: